First try a power reset. This is done by, unplugging your laptop and remove the battery then holding the power switch down for 30 seconds. If this does not work, keep moving through the troubleshooting options shown below.

Look at the screen from another perspective. Is the screen showing any signs of light? If there is any light at all it may be a problem, with the backlight.

Also try cycling all the options on the moniter selection button on the key board. The moniter may be black because it is on a setting that goes to another monitor.

If the probelm persists, then you may need to replace the ballast, the power source of the backlight.

First, try to boot into Safe Mode by pressing the key (usually F8) displayed during boot. If this works, do a "System Restore" to roll back your OS to an earlier version. If this doesn't work, perform a "Repair Install" using the Windows disk supplied by Sony.

If your computer turns on but does not boot the OS(operating system) when you press the power button it may well be a bad RAM issue, and you may need to follow install new RAM. The computer BIOS usually lets the user know when RAM is the problem it beeps 3 times.If that is the case you need to replace the RAM.

If none of the above have worked, you may have hard disk errors. Put your hard drive in another computer and see if it works (make sure to backup your files now if you couldn't do this in your original computer).You may be experiencing a boot file corruption and that can be easily fixed with a recovery disk.Also the hard drive may have been damaged by contact with a magnetic tool and that may have erased the hard drive completely, also a hard fall is enough to damage a drive. Try replacing your hard drive to see if its the problem.